PRINCIPLES OF NAVAL ENGINEERING 



COIL AND CORE ASSEMBLY 



147.125 



Figure 20-21,— Single-phase transformer. 



for gunfiring circuits, special signal lights, and 

 high-voltage ignition circuits. 



The typical transformer has two windings 

 which are electrically insulated from each other. 

 These windings are wound on a common mag- 

 netic circuit made of laminated sheet steel. 

 The principal parts are the core , which provides 

 a circuit of low reluctance for the magnetic 

 flux; the primary winding , which receives the 

 energy from the a-c source; and the secondary 

 winding , which receives the energy by mutual 

 induction from the primary and delivers it to 

 the load. 



When a transformer is used to step up the 

 voltage, the low-voltage winding is the primary. 

 When a transformer is used to step down the 

 voltage, the high- voltage winding is the primary. 

 The primary is always connected to the source 

 of the power; the secondary is always connected 

 to the load. It is common practice to refer to the 

 windings as the primary and the secondary, 



rather than as the high-voltage and the low- 

 voltage windings. 



The operation of the transformer is based 

 on the principle that electrical energy can be 

 transferred efficiently by mutual induction from 

 one winding to another. When the primary wind- 

 ing is energized from an a-c source, an alter- 

 nating magnetic flux is established in the trans- 

 former core. This flux links the turns of both 

 primary and secondary, thereby inducing volt- 

 ages in them. Because the same flux cuts both 

 windings, the same voltage is induced in each 

 turn of both windings. Hence the total induced 

 voltage in each winding is proportional to the 

 number of turns in that winding. That is, 



'1 



Ni 



E2 N2 



where E-^ and E2 are the induced voltages in the 

 primary and secondary windings, respectively, 



508 



